1. Field of the Invention
This invention is generally directed to automatically operated drain valves, and, more particularly, to a drain valve operated by the use of a counterweight.
2. Description of the Related Art
Semiconductor devices are manufactured using a series of complex steps that normally employ a variety of chemicals in both liquid and gaseous form. These chemicals include some relatively corrosive liquids and gases, such as hydrochloric acid. Hydrochloric acid is not entirely consumed by the process of manufacturing the semiconductor devices, and thus must be disposed of. Commonly, special drain systems are included adjacent the manufacturing equipment so that liquids may be efficiently removed.
Ordinarily, conventional drain systems include a P-trap to prevent gases from escaping. The P-trap captures a small portion of the waste liquid and uses it to substantially seal the drainpipe at least from leakage of gas. However, in a drain system that is intended to handle volatile chemicals such as hydrochloric acid, P-traps may not be employed. For example, if the P-trap were to fill with hydrochloric acid during one step of the semiconductor manufacturing process, and then in a subsequent step water were introduced to the P-trap, an undesirable violent reaction could occur.
Since P-traps may not be used on these types of drain systems, corrosive gases may be re-introduced to the area via the drainpipe, or even transported to other areas by the drain system. The introduction of corrosive gases into the manufacturing environment has obvious environmental consequences, including damage to expensive and sensitive equipment.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.